Robert Rowthorn (in his Communist party days, he was plain Bob) has returned to his role as immigration Cassandra. In a comment piece in the Sunday Telegraph, he warns of the problems caused by foreigners arriving in Britain.

More specifically, he portentously announces that "as an academic economist" he believes there are no economic benefits to be derived from large-scale immigration; that on the contrary, many immigrants have "no skills" and clog up doctors' surgeries. They also apparently threaten the existence of the countryside in the south-east of England, and will "completely change the culture and complexion of many cities".

There are a number of oddities in Rowthorn's economic analysis. One might have expected him to address the issue of where, in a globalised economy (he suggests no restraint on the movement of goods or capital), labour would be most productive. Nor does he grapple with the issue of resolving the global inequalities that drive much economic migration.

And his dismissal of the argument that immigration could help solve the pensions crisis is absurd. He suggests that this has no validity because migrants get old too. Where would we be without the insights of academic economists?

Does the professor not think that the question of the economically active proportion of migrant households - ie more people paying into the system for longer, relative to the rest of the population - may have some bearing on the question? But then, I am no academic.

Professor Rowthorn's main argument, however, is that immigrants work too hard for too little money and put up with worse working conditions. In a touch of demagogy - let no-one say that "academic economists" are above that kind of thing - he alleges that this only benefits the "nanny- and house cleaner-using classes". When he was a Marxist, he might have said it only benefits the bourgeoisie, but I suppose that wouldn't do for the Sunday Telegraph.

To that extent, he would be right. Many migrant workers do suffer the most rapacious exploitation. One could address that in a variety of ways: by raising the minimum wage (and properly enforcing it) or by restoring a proper system of workplace inspection; by regularising the position of migrant workers - living in a legal grey area makes them doubly vulnerable; or by supporting the trade union effort to organise all workers so that one group does not undercut the other.

But the professor does not advocate any of these things. His implied message is clear: stop them coming here. I assume he has always cleaned his own house. If so, that, rather than his reactionary opinions, would make him unique among Cambridge dons.

His central argument is, of course, exactly the same as that deployed against the Irish in the 19th century, against Jewish workers early in the 20th and against black and Asian workers after the second world war. In each case, the trade union movement responded (invariably belatedly) by extending protection and organisation to migrant workers so that unscrupulous capitalists could not take advantage of divisions in the working-class.

The answer to exploitation is trade union organisation and legal improvements, not strengthening an already oppressive system of coercion that should scandalise any civilised country.

Rowthorn would once have understood this. Now he prefers to close the door. Perhaps he would prefer it if our green and pleasant land had never been polluted by Irish, Jewish and Afro-Caribbean workers. I do not know. But that would be the logic of his argument. (Sunday Telegraph readers are attuned to nudges and winks on matters like this.)

At any event, the good professor asserts that there is something called an "immigration lobby" - undefined, very sloppy - that brands arguments like his "racist". Why would that be? Let the debate begin.